800 KVA Delta Wye Grounded Transformer-34.5/0.48 KV | USA 2025

Safety meets simplicity: pad mounted transformer for smart urban grids.

01 General

1.1 Project Description

800 kVA three phase pad mounted transformer was delivered to USA in 2025. The rated power of the transformer is 800 kVA with KNAN cooling. The high voltage is 34.5GrdY/19.92 kV with ±2*2.5% tapping range (NLTC), the low voltage is 0.48 kV, they formed a vector group of YNd1.

This 800 kVA delta wye grounded transformer is manufactured by SCOTECH. in accordance with IEEE Std C57.12.34-2022. Designed for three-phase, 60 Hz underground distribution systems, it features a primary voltage of 34.5 kV (grounded wye) and a secondary voltage of 480 V delta, with a YNd1 vector group. A notable design aspect is the separately brought out H0 (neutral) bushing on the high-voltage side, which facilitates convenient system grounding and simplifies network integration.

The delta wye grounded transformer adopts KNAN as its cooling method, utilizing FR3 natural ester fluid as both dielectric and cooling medium. This combination provides reliable heat dissipation while offering enhanced fire safety and environmental benefits compared to conventional mineral oil. For primary-side overcurrent protection, the unit is equipped with high-quality Cooper (Eaton) bayonet fuses and current-limiting backup fuses, ensuring effective fault clearing and robust protection for downstream equipment.

Additionally, this transformer meets the U.S. Department of Energy (DOE) efficiency standards, ensuring compliance with federal energy regulations and delivering lower no‑load and load losses, which translates into reduced operational energy costs. Suitable for residential subdivisions, commercial complexes, and industrial facilities, this pad-mounted transformer combines robust electrical performance, proven protective components, and energy-efficient operation in a compact, outdoor-ready enclosure.

1.2 Technical Specification

800 kVA delta wye grounded transformer specifications type and data sheet

1.3 Drawings

800 kVA delta wye grounded transformer diagram drawing and size.

02 Manufacturing

2.1 Core

The core is built with high-permeability, low-loss cold-rolled grain-oriented silicon steel in a three-leg configuration that optimizes the magnetic path. After automated stacking and vacuum annealing, the measured no‑load loss is only 0.992 kW at 20°C, better than the guaranteed value of 1.1 kW, and complies with IEEE C57.12.00‑2021 and C57.12.34‑2022. The stable and consistent results from no‑load loss and excitation current tests confirm a well‑designed magnetic circuit and high manufacturing uniformity. Step‑lap stacking and tight flux density control help keep both losses and audible noise low.

2.2 Winding

Both high‑voltage and low‑voltage windings are made of copper and arranged in a YNd1 vector group, with the H0 bushing brought out separately for easy neutral grounding. The ratio deviation is between –0.03% and 0.04%, well within the ≤0.5% limit, and the maximum resistance unbalance on the LV side is only 3.24%, reflecting precise turn distribution and tension control. All ratio, phase‑relation and insulation resistance tests performed to IEEE C57.12.90‑2021 were passed – the HV‑LV to ground insulation resistance reached 3.45 GΩ. Automatic tension control and inter‑layer insulation pressing during winding ensure consistency and dielectric strength between turns and layers.

2.3 Tank

The tank is fabricated from high‑strength steel with a corrosion‑resistant coating suitable for outdoor pad‑mounted environments. It passed a 24‑hour static pressure test at 20 kPa with no leakage or permanent deformation, fully meeting IEEE C57.12.90‑2021. This verifies the quality of the welds and flange seals. Automated welding, 100% light leak inspection, and a pre‑shipment pressure test guarantee that no oil leakage or insulation degradation will occur over long‑term service.

2.4 Final Assembly

Final assembly is carried out in a clean room; FR3 insulating oil is vacuum‑treated and filtered before filling, and the cooling method is KNAN. The rated parameters – 800 kVA / 34.5 kV / 480 V / 60 Hz – exactly match the design, and the complete transformer complies with IEEE C57.12.34‑2022. After assembly, the insulation resistance (HV‑LV to ground) measured 3.45 GΩ, far above safety thresholds. Key process points are checked during assembly, oil treatment is monitored in real time for moisture content and dielectric strength, and modular pre‑assembly combined with clean‑room control effectively prevents contamination, ensuring long‑term insulation reliability.

03 Testing

All routine tests performed to IEEE C57.12.90‑2021 gave excellent results: no‑load loss 0.992 kW, load loss at 85°C 5.345 kW (both better than guaranteed values), short‑circuit impedance 5.64% (within ±7.5% tolerance), and efficiency 99.45% (exceeding the 99.40% requirement and meeting DOE efficiency standards). The applied withstand test (LV side 10 kV/60 s) and induced voltage test (HV side 69 kV/48 s) showed no breakdown, and neither the insulation resistance nor the 24‑hour seal test revealed any anomaly. All tests passed on the first run, demonstrating ample reliability margins in both electrical and mechanical performance.

04 Packing and Shipping

4.1 Packing

The delta wye grounded transformer is packed in a strong wooden or steel frame with shock‑absorbing material inside, and all terminals are protected against moisture and dust. The outside of the package is clearly marked with the model, weight, and handling instructions, and the packaging meets the protection requirements for sea and land transport. Before packing, each transformer receives a final cleaning and tightening check; the packaging design has been validated by drop and vibration simulation tests to keep the unit intact during long‑distance shipping. For export orders, ISPM‑15 compliant or eco‑friendly packaging materials can be provided.

4.2 Shipping

The transformer is shipped from our factory in Jiangshan, Zhejiang, and can be delivered by sea or land. We provide full export documentation, including customs clearance papers and certificates of origin. With years of experience exporting pad‑mounted transformers to North America, we can flexibly arrange transport according to your project schedule. A simulated transport vibration test is performed before shipment, professional cargo insurance is arranged, and GPS tracking is available throughout the journey. A standardized logistics process shortens lead times and reduces the risk of in‑transit damage.

05 Site And Summary

At SCOTECH, our pad-mounted transformers deliver unmatched reliability and efficiency for modern power distribution networks. Engineered with a fully sealed, corrosion-resistant enclosure and advanced low-loss cores, they ensure continuous, maintenance-friendly operation that lowers total ownership cost and maximizes uptime. Every unit reflects our commitment to precision and adaptability, offering tailored voltage ratings, enhanced safety configurations, and strict quality assurance. Backed by responsive after-sales support, our transformers not only meet but redefine industry benchmarks. Trust SCOTECH to engineer the resilience and performance your critical infrastructure deserves.